Current measuring devices of a clamp-on or proximity-type are known. Such devices have historically been used to make current measurements in situations where it has been either impractical or undesirable for one reason or another, such as high voltage and/or high current applications, to use directly coupled current measuring instruments. Depending on the application, other parameters or total harmonic distortion (THD) may in fact be more important than amplitude of the composite current waveform.
There continues to be a need for non-contact harmonic distortion measuring instruments which provide information about the ratio of the amplitudes of harmonics present in the current or voltage waveform being measured as well as distortion information. Preferably, such instruments would use a non-contact measuring technique in combination with analysis circuitry for providing real-time read outs of relative amplitude values of harmonics present in the signal being measured along with indicia of harmonic distortion.